U.S. patent number 10,890,122 [Application Number 16/344,540] was granted by the patent office on 2021-01-12 for method and device for controlling starting of engine.
This patent grant is currently assigned to Mazda Motor Corporation. The grantee listed for this patent is Mazda Motor Corporation. Invention is credited to Kanae Fuki, Ryohei Karatsu, Toru Kobayashi, Takamitsu Miyahigashi, Hiromu Sugano, Kotaro Takahashi, Masahiro Tateishi, Jiro Yamasaki.
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United States Patent |
10,890,122 |
Fuki , et al. |
January 12, 2021 |
Method and device for controlling starting of engine
Abstract
At start of an engine, a fuel injection amount is set to a
jump-over injection amount if the engine speed obtained in each
cycle is higher than or equal to a determination threshold value,
which is set lower than a lower limit of a resonance speed range of
powertrain by a predetermined reference value. If the engine speed
is lower than the value, the fuel injection amount is set to a
step-over injection amount that is smaller than the jump-over
injection amount. This setting makes it possible to increase the
engine speed such that the engine speed approaches the lower limit
of the resonance speed range causing resonance in the powertrain,
up to a predetermined range, and then causes the engine speed to
jump straight to an engine speed which exceeds the resonance speed
range, while in the process of increasing the engine speed by
executing the combustion cycles.
Inventors: |
Fuki; Kanae (Otake,
JP), Takahashi; Kotaro (Hiroshima, JP),
Kobayashi; Toru (Hiroshima, JP), Sugano; Hiromu
(Higashihiroshima, JP), Tateishi; Masahiro
(Hatsukaichi, JP), Karatsu; Ryohei (Hiroshima,
JP), Miyahigashi; Takamitsu (Kure, JP),
Yamasaki; Jiro (Higashihiroshima, JP) |
Applicant: |
Name |
City |
State |
Country |
Type |
Mazda Motor Corporation |
Hiroshima |
N/A |
JP |
|
|
Assignee: |
Mazda Motor Corporation
(Hiroshima, JP)
|
Family
ID: |
1000005295482 |
Appl.
No.: |
16/344,540 |
Filed: |
November 30, 2016 |
PCT
Filed: |
November 30, 2016 |
PCT No.: |
PCT/JP2016/085639 |
371(c)(1),(2),(4) Date: |
April 24, 2019 |
PCT
Pub. No.: |
WO2018/100698 |
PCT
Pub. Date: |
June 07, 2018 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
|
US 20190293005 A1 |
Sep 26, 2019 |
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F02D
41/062 (20130101); F02D 41/40 (20130101); F02D
29/02 (20130101); F02N 11/00 (20130101); F02D
2200/1002 (20130101); F02D 2200/101 (20130101); F02D
2250/18 (20130101); F02D 2200/50 (20130101); F02D
2250/28 (20130101); F02P 5/15 (20130101); Y02T
10/40 (20130101) |
Current International
Class: |
F02D
41/08 (20060101); F02D 41/06 (20060101); F02N
11/00 (20060101); F02D 41/40 (20060101); F02D
29/02 (20060101); F02P 5/15 (20060101) |
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Other References
European Patent Office, Extended European Search Report Issued in
Application No. 18213940.2, dated Jun. 11, 2019, Germany, 88 pages.
cited by applicant.
|
Primary Examiner: Moulis; Thomas N
Attorney, Agent or Firm: Alleman Hall Creasman & Tuttle
LLP
Claims
The invention claimed is:
1. A method of controlling start of an engine from when cranking is
started by driving a starter motor until when an engine speed
reaches a predetermined idle speed by execution of combustion
cycles, the method comprising: a step of obtaining the engine speed
in each cycle; and a step of setting a torque based on the engine
speed obtained in the step of obtaining the engine speed, wherein
in the step of setting the torque, a first torque is set as the
torque, if a difference between a lower limit of a preset resonance
speed range including an engine speed corresponding to a resonance
frequency of a powertrain unit including the engine and the engine
speed obtained in the step of obtaining the engine speed is smaller
than a predetermined reference value, and a second torque smaller
than the first torque is set as the torque, if the difference is
larger than or equal to the reference value.
2. The method of claim 1, wherein in the step of setting the
torque, if the difference is larger than or equal to the reference
value, the torque is set so that the engine speed achievable by
combustion in one of the combustion cycles, the engine speed of
which combustion cycle has been obtained to have the difference, is
lower than the lower limit of the resonance speed range, and so
that the difference becomes smaller than the reference value.
3. The method of claim 1, wherein the engine is a 4-cylinder,
4-cycle engine, and in the step of obtaining the engine speed, a
rotation speed of a crankshaft provided in the engine is detected
when a cylinder executing an n-th combustion cycle is in a first
half of a compression stroke of the combustion cycle, where n is a
positive integer, and the engine speed achieved by combustion in an
(n-1)-th combustion cycle is obtained based on the rotation
speed.
4. The method of claim 1, wherein the engine is a compression
ignition engine which includes at least one injector configured to
inject fuel to be fed into a combustion chamber, and which ignites
the fuel fed into the combustion chamber by a compression operation
of a piston, the step of setting the torque is a step of setting an
amount of fuel to be injected by the injector in accordance with
the difference, and in the step of setting the amount of fuel, a
first predetermined injection amount is set as the amount of fuel
to be injected, if the difference is smaller than the reference
value, and a second injection amount, which is smaller than the
first injection amount, is set as the amount of fuel to be
injected, if the difference is larger than or equal to the
reference value.
5. The method of claim 4, wherein an amount of intake air to be
introduced into the combustion chamber, and a temperature inside
the combustion chamber are obtained, and in the step of setting the
amount of fuel, if the difference is smaller than the reference
value, the first injection amount is set to allow the engine to
output a maximum torque corresponding to the amount of intake air
to be introduced to the combustion chamber and the temperature
inside the combustion chamber.
6. The method of claim 4, wherein in the step of setting the amount
of fuel, if the difference is smaller than the reference value, the
first injection amount is set such that the engine speed increases
at a maximum rate by combustion of the combustion cycles in a start
period from start of the combustion cycles until the engine speed
reaches the idle speed.
7. A system for controlling start of an engine comprising: a
starter motor which rotates a crankshaft provided in the engine; an
injector attached to the engine, and configured to inject fuel to
be fed into a combustion chamber; a controller connected to each of
the starter motor and the injector, and configured to output a
control signal to each of the starter motor and the injector to
operate the engine; an engine speed sensor connected to the
controller, and configured to detect an engine speed and output a
detection signal to the controller; wherein the controller
includes: a speed obtaining section which obtains the engine speed
in each of cycles based on the detection signal of the engine speed
sensor; and a fuel amount setting section which sets, based on the
engine speed obtained by the speed obtaining section, an amount of
fuel to be injected by the injector, and the fuel amount setting
section sets: in a start period of the engine from when cranking is
started by driving the starter motor until when the engine speed
reaches a predetermined idle speed by execution of the combustion
cycles, a first injection amount as the amount of fuel to be
injected, if a difference between a lower limit of a preset
resonance speed range including an engine speed corresponding to a
resonance frequency of a powertrain unit including the engine and
the engine speed obtained by the speed obtaining section is smaller
than a predetermined reference value; and a second injection
amount, which is smaller than the first injection amount, as the
amount of fuel to be injected, if the difference is larger than or
equal to the reference value.
8. The system of claim 7, wherein, if the difference is larger than
or equal to the reference value, the fuel amount setting section
sets the second injection amount so that the engine speed
achievable by combustion in one of the combustion cycles, the
engine speed of which combustion cycle has been obtained to have
the difference, is lower than the lower limit of the resonance
speed range, and so that the difference becomes smaller than the
reference value.
9. The system of claim 7, wherein, the engine is a 4-cylinder,
4-cycle engine, and the speed obtaining section detects a rotation
speed of a crankshaft when a cylinder executing an n-th combustion
cycle is in a first half of a compression stroke of the combustion
cycle, and obtains the engine speed achieved by combustion in an
(n-1)-th combustion cycle based on the rotation speed of the
crankshaft, where n is a positive integer.
10. The system of claim 7, wherein the engine is a compression
ignition engine which ignites fuel fed into the combustion chamber
by a compression operation of a piston.
11. The system of claim 10, further comprising: an airflow sensor
which detects a flow rate of intake air flowing through an intake
passage provided in the engine; and a water temperature sensor
which is attached to the engine, and detects a temperature of
engine cooling water, wherein the controller obtains an amount of
intake air to be introduced to the combustion chamber based on a
detection signal of the airflow sensor, and obtains a temperature
inside the combustion chamber based on a detection signal of the
water temperature sensor, and if the difference is smaller than the
reference value, the fuel amount setting section sets the first
injection amount so as to allow the engine to output a maximum
torque corresponding to the amount of intake air to be introduced
to the combustion chamber and the temperature inside the combustion
chamber.
12. The system of claim 10, wherein, if the difference is smaller
than the reference value, the fuel amount setting section sets the
first injection amount such that the engine speed increases at a
maximum rate by combustion of the combustion cycles in a start
period from start of the combustion cycles until the engine speed
reaches the idle speed.
Description
TECHNICAL FIELD
The technique disclosed herein relates to a method of and a system
for controlling start of an engine.
BACKGROUND ART
An engine is integrated with a power transmission mechanism such as
a transmission to form a powertrain unit called "powertrain," which
is mounted in a vehicle body via an engine mount having elastic
force. While the engine operates, the movement of the engine
generates vibrations of the powertrain. If the frequency of these
vibrations is equal to the resonance frequency (i.e. the natural
frequency) of the powertrain, resonance occurs. Then, the
vibrations generated in the powertrain are not damped enough by the
engine mount, and thereby increasing the vibrations transmitted to
the vehicle and the accompanying noise. This makes the occupant(s)
uncomfortable.
The frequency of the vibrations generated in a powertrain by
driving of an engine corresponds to the engine speed. Resonance
occurs in the powertrain while the vehicle travels in a condition
in which a speed range at and around an engine speed causing
resonance in the powertrain (hereinafter referred to as a
"resonance speed range") is set higher than or equal to an engine
speed while an engine performs a no-load operation, what is called
an "idle operation," in which no driving power is transmitted to
driving wheels (tires) after the start of the engine (hereinafter
referred to as an "idle speed"). For this reason, the powertrain is
usually designed so that the resonance speed range falls within a
speed range lower than the idle speed.
If, in this manner, the resonance speed range causing resonance in
the powertrain is set to the engine speed range lower than the idle
speed, the above-described resonance in the powertrain may generate
vibrations in the vehicle at the start period of the engine, which
is from when the engine starts cranking until when execution of
combustion cycles allows the engine speed to reach the idle speed.
To address the problem, techniques of reducing vibrations of a
vehicle at start of an engine have been suggested.
For example, Patent Document 1 discloses an engine control system
(an ignition timing control system) that performs ignition at
unique timing at start of the engine. This control system is
configured to advance the ignition timing in a period immediately
after the start of the engine until the engine speed passes through
the resonance speed range (or a vehicle resonance band), compared
with the ignition timing in the idle operation. According to this
configuration, the engine torque increases by the advance of the
ignition timing. This accelerates the engine speed at a higher rate
and allows the operating state of the engine to rapidly pass
through the resonance speed range.
CITATION LIST
Patent Document
Patent Document 1: Japanese Unexamined Patent Publication No.
2015-113774
SUMMARY OF THE INVENTION
Technical Problem
As in the engine control system disclosed in Patent Document 1, an
increase in the engine torque at the start of the engine allows the
operating state of the engine to rapidly pass through the resonance
speed range. However, while the engine speed increases, the engine
speed achieved by combustion in each combustion cycle may fall
within the resonance speed range causing resonance in the
powertrain. Vibrations are inevitably generated in the powertrain
by resonance. If the resonance in the powertrain causes vibrations
of the vehicle even for a short time, the occupant(s) of the
vehicle feel(s) uncomfortable.
Particularly, a compression ignition engine including a diesel
engine has a compression ratio higher than a general spark ignition
engine. The torque therefore varies relatively largely at
combustion in each combustion cycle, which causes relatively large
vibrations in the engine. If the engine speed achieved by
combustion in each combustion cycle falls within the resonance
speed range causing resonance in the powertrain, the vibrations
caused by the resonance in the powertrain and the vibrations caused
by the torque variations at that time together increase the
vibrations generated in the powertrain. As a result, significant
vibrations are generated in the vehicle.
The technique disclosed herein is therefore intended to reduce
vibrations generated in a powertrain unit including an engine at
start of the engine.
Solution to the Problem
In order to achieve the above objective, the technique disclosed
herein increases the engine speed such that the engine speed
approaches the lower limit of a resonance speed range causing
resonance in a powertrain unit, up to a predetermined range, and
then causes the engine speed to jump straight to an engine speed
which exceeds the resonance speed range, while in a process of
increasing the engine speed by executing combustion cycles.
Specifically, the technique disclosed herein is directed to a
method of controlling start of an engine from when cranking is
started by driving a starter motor until when an engine speed
reaches a predetermined idle speed by execution of combustion
cycles. The method of controlling start of the engine includes a
step of obtaining the engine speed in each cycle, and a step of
setting a torque based on the engine speed obtained in the step of
obtaining the engine speed.
In the step of setting the torque, a first torque is set as the
torque, if a difference between a lower limit of a preset resonance
speed range including an engine speed corresponding to a resonance
frequency of a powertrain unit including the engine and the engine
speed obtained in the step of obtaining the engine speed is smaller
than a predetermined reference value, and a second torque smaller
than the first torque is set as the torque, if the difference is
larger than or equal to the reference value.
In this method of controlling start of the engine, the combustion
cycles are executed after cranking has been started by driving the
starter motor. Once the combustion cycles start, the engine speed
is obtained in each cycle in the step of obtaining the engine
speed. Then, in the step of setting the torque, a torque is set as
a targeted control variable based on the engine speed obtained in
the step of obtaining the engine speed. At the start of the engine,
a rate of increase in the engine speed varies depending on the
magnitude of the torque set in the above manner. The larger the
torque is, the more the engine speed increases, while the smaller
the torque is, the less the engine speed increases.
In the step of setting the torque, if the difference between the
engine speed obtained in the step of obtaining the engine speed and
the lower limit of the resonance speed range is larger than or
equal to the predetermined reference value, the engine speed is
lower than, and is relatively far from, the lower limit of the
resonance speed range. The engine torque is thus set to the second
torque that is relatively small. Since the second torque is smaller
than the first torque, the rate of increase in the engine speed is
small. The engine speed can thus approach the lower limit of the
resonance speed range before the engine speed exceeds the resonance
speed range.
On the other hand, in the step of setting the torque, if the
difference between the engine speed obtained in the step of
obtaining the engine speed and the lower limit of the resonance
speed range is smaller than the reference value, the engine speed
is relatively close to the lower limit of the resonance speed
range. The engine torque is thus set to the first torque that is
relatively large. Since the first torque is larger than the second
torque, the engine speed can be increased more significantly from
the engine speed close to the lower limit of the resonance speed
range.
In this manner, the method of controlling start of the engine makes
it possible to increase the engine speed such that the engine speed
approaches the lower limit of the resonance speed range, up to a
predetermined range, and then increase the engine speed
significantly, while in the process of increasing the engine speed
by executing the combustion cycles. This reduces the possibility
that the engine speed achieved by the combustion in each combustion
cycle falls within the resonance speed range. The resonance, which
may occur in the powertrain unit including the engine at the start
of the engine, can be thus reduced.
In the step of setting the torque, if the difference is larger than
or equal to the reference value, the torque may be set so that the
engine speed achievable by combustion in one of the combustion
cycles, the engine speed of which combustion cycle has been
obtained to have the difference, is lower than the lower limit of
the resonance speed range, and so that the difference becomes
smaller than the reference value.
In such a method of controlling start of the engine, if the engine
speed after start of the combustion cycles is lower than and
relatively far from the lower limit of the resonance speed range,
the torque is set such that the engine speed approaches the lower
limit of the resonance speed range, up to a predetermined range in
which the engine torque is set to the first torque. As a result,
the engine speed which has been relatively far from the lower limit
of the resonance speed range can efficiently approach the lower
limit in a smaller number of combustion cycles. This is thus
advantages in rapid ending of the start of the engine.
The engine may be a 4-cylinder, 4-cycle engine. In this case, in
the step of obtaining the engine speed, a rotation speed of a
crankshaft may be detected when a cylinder executing an n-th
combustion cycle is in a first half of a compression stroke of the
combustion cycle, where n is a positive integer, and the engine
speed achieved by combustion in an (n-1)-th combustion cycle may be
obtained based on the rotation speed.
The "first half of a compression stroke" used herein corresponds to
the first half of a compression stroke when the compression stroke
is divided into the first and second halves. Note that the number
of the "combustion cycles" used herein is not counted up
independently for each cylinder, but is counted up for all the four
cylinders together. Specifically, in a 4-cylinder, 4-cycle engine,
the number of combustion cycles is incremented by one every time
the crankshaft turns 180 degrees.
In a conceivable method of obtaining the engine speed, the engine
speed may be detected based on, for example, the time required by
the crankshaft to turn 180 degrees of one rotation (360 degrees),
that is, the speed of a half rotation of the crankshaft. Such a
method of obtaining the engine speed is advantageous in securing
high accuracy in detecting the engine speed in a normal operating
state, in which the engine operates at a speed higher than or equal
to the idle speed, because rotation speed of the crankshaft at this
moment is higher than at the start of the engine.
However, at the start of the engine, variations in the engine speed
due to combustion of each combustion cycle are relatively large,
compared to the time when the engine operates at a speed higher
than the idle speed, because there is a great influence of the
inertia of the flywheel. Thus, if the time required by the
crankshaft to turn 180 degrees (i.e., a half rotation) is used to
obtain the engine speed, the accuracy in detecting the engine speed
rather deteriorates. For this reason, the method of obtaining the
engine speed based on the speed of the half rotation of the
crankshaft is not suitable as a method of obtaining the engine
speed achieved by the combustion in the previous (n-1)-th
combustion cycle, before the setting of the fuel injection amount
in the n-th combustion cycle at the start of the engine.
By contrast, the method according to the technique disclosed herein
detects the engine speed achieved by the combustion in the (n-1)-th
combustion cycle based on the rotation speed of the crankshaft in
the first half of the compression stroke in the n-th combustion
cycle.
In a 4-cylinder, 4-cycle engine, when combustion is performed in
the (n-1)-th combustion cycle, that is, when the cylinder executing
this combustion cycle is in an expansion stroke, the cylinder
executing the n-th combustion cycle is in a compression stroke.
Thus, the engine speed achievable by the combustion in the (n-1)-th
combustion cycle can be obtained by obtaining the rotation speed of
the crankshaft when the cylinder executing the n-th combustion
cycle is in the compression stroke. In particular, by obtaining the
engine speed in the first half of the compression stroke, the
information of the engine speed achieved by the combustion in the
(n 1)-th combustion cycle can be reflected in the setting of the
torque in the n-th combustion cycle, and further in a control
operation of the manipulation according to the torque.
The engine may be a compression ignition engine which includes an
injector configured to inject fuel to be fed into a combustion
chamber, and which ignites the fuel fed into the combustion chamber
by a compression operation of a piston, In this case, the step of
setting the torque may be a step of setting an amount of fuel to be
injected by the injector in accordance with the difference. In the
step of setting the amount of fuel, a first predetermined injection
amount may be set as the amount of fuel to be injected, if the
difference is smaller than the reference value, and a second
injection amount smaller than the first injection amount may be set
as the amount of fuel to be injected, if the difference is larger
than or equal to the reference value.
The "compression ignition engine" used herein includes a diesel
engine and a compression ignition gasoline engine. The "combustion
chamber" used herein is not limited to a space defined when the
piston reaches a compression top dead center. The term "combustion
chamber" is used in a broad sense.
In a compression ignition engine, the torque varies depending on
the amount of fuel fed into the combustion chamber. The more fuel
is injected, the larger torque of the engine is obtained, while the
less fuel is injected, the smaller torque of the engine is
obtained. Thus, setting, in the step of setting the amount of fuel,
the amount of fuel to be injected in accordance with the difference
between the engine speed and the lower limit of the resonance speed
range allows the engine to obtain a torque corresponding to the
amount of fuel to be injected. Specifically, if the first injection
amount is set as the amount of fuel to be injected, the engine
obtains the first torque, which is relatively large, as a torque
corresponding to the first injection amount. On the other hand, if
the second injection amount is set as the amount of fuel to be
injected, the engine obtains the second torque, which is relatively
small, as a torque corresponding to the second injection
amount.
In the method of controlling start of the engine, an amount of
intake air to be introduced into the combustion chamber, and a
temperature inside the combustion chamber may be obtained. In this
case, in the step of setting the amount of fuel, if the difference
is smaller than the reference value, the first injection amount may
be set to allow the engine to output a maximum torque corresponding
to the amount of intake air to be introduced to the combustion
chamber and the temperature inside the combustion chamber.
The torque of an engine can be obtained by burning fuel in the air.
The amount of intake air to be introduced into the combustion
chamber, together with the amount of fuel to be injected by the
injector, is a factor changing the combustion pressure, thereby
influencing the torque obtained in the engine. The temperature
inside the combustion chamber influences the volatility of a fuel
(how easily the fuel evaporates), and is thus also a factor
changing the combustion pressure, thereby influencing the torque
obtained in the engine. Therefore, the maximum torque that can be
output by the engine is determined mainly depending on the amount
of intake air introduced into the combustion chamber and the
temperature inside the combustion chamber.
In the step of setting the amount of fuel, if the difference
between the engine speed and the lower limit of the resonance speed
range is smaller than the predetermined reference value, that is,
if the engine speed is relatively close to the lower limit of the
resonance speed range, the first injection amount is set such that
the engine outputs the maximum torque. As a result, the engine
speed suddenly increases due to the maximum torque obtained by the
comparison according to the first injection amount. This allows the
engine speed achieved by the combustion at this moment to jump over
the resonance speed range and fall out of the resonance speed
range.
In the step of setting the amount of fuel, if the difference is
smaller than the reference value, the first injection amount may be
set such that the engine speed increases at a maximum rate by
combustion of the combustion cycles in a start period from start of
the combustion cycles until the engine speed reaches the idle
speed.
In the step of setting the amount of fuel, if the difference
between the engine speed and the lower limit of the resonance speed
range is smaller than the reference value, that is, if the engine
speed is relatively close to the lower limit of the resonance speed
range, the first injection amount is set such that the engine speed
increases at a maximum rate in the start period. As a result, the
engine speed increases as significantly as possible due to the
torque obtained by the comparison according to the first injection
amount. This allows the engine speed achieved by the combustion at
this moment to jump over the resonance speed range and fall out of
the resonance speed range.
The technique disclosed herein is also directed to a system of
controlling start of an engine from when cranking is started by
driving a starter motor until when an engine speed reaches a
predetermined idle speed by execution of combustion cycles. The
system for controlling start of the engine includes: a starter
motor which rotates a crankshaft provided in the engine; an
injector attached to the engine, and configured to inject fuel to
be fed into a combustion chamber; a controller connected to each of
the starter motor and the injector, and configured to output a
control signal to each of the starter motor and the injector to
operate the engine; and an engine speed sensor connected to the
controller, and configured to detect an engine speed and output a
detection signal to the controller.
The controller includes: a speed obtaining section which obtains
the engine speed in each cycle based on the detection signal of the
engine speed sensor; and a fuel amount setting section which sets,
based on the engine speed obtained by the speed obtaining section,
an amount of fuel to be injected by the injector. the fuel amount
setting section sets, in a start period of the engine from when
cranking is started by driving the starter motor until when the
engine speed reaches an idle speed by execution of the combustion
cycles, a first injection amount as the amount of fuel to be
injected, if a difference between a lower limit of a preset
resonance speed range including an engine speed corresponding to a
resonance frequency of a powertrain unit including the engine and
the engine speed obtained by the speed obtaining section is smaller
than a predetermined reference value, and a second injection
amount, which is smaller than the first injection amount, as the
amount of fuel to be injected, if the difference is larger than or
equal to the reference value.
In this system for controlling start of the engine, the combustion
cycles are executed after cranking has been started by driving the
starter motor. Once the combustion cycles start, the speed
obtaining section obtains the engine speed in each cycle. The fuel
amount setting section sets, based on the engine speed obtained by
the speed obtaining section, the amount of fuel to be injected by
the injector. The engine torque is determined depending on the
amount of fuel set at this moment, and the rate of increase in the
engine speed varies. The larger the fuel injection amount is, the
more the engine speed increases, while the smaller the fuel
injection amount is, the less the engine speed increases.
If the difference between the engine speed obtained by the speed
obtaining section and the lower limit of the resonance speed range
is larger than or equal to the reference value, the engine speed is
lower than and relatively far from the lower limit of the resonance
speed range. The fuel injection amount is therefore set to the
second injection amount that is relatively small. Since the second
injection amount is smaller than the first injection amount, this
setting reduces the torque, and eventually the rate of increase in
the engine speed. The engine speed can thus approach the lower
limit of the resonance speed range before the engine speed exceeds
the resonance speed range.
On the other hand, if the difference between the engine speed
obtained by the speed obtaining section and the lower limit of the
resonance speed range is smaller than the reference value, the
engine speed is relatively close to the lower limit of the
resonance speed range. Thus, the fuel injection amount is set to
the first injection amount that is relatively large. Since the
first injection amount is larger than the second injection amount,
this setting increases the torque, and eventually the rate of
increase in the engine speed.
In this manner, the system for controlling start of the engine
makes it possible to increase the engine speed such that the engine
speed approaches the lower limit of the resonance speed range, and
then significantly increase the engine speed, while in the process
of increasing the engine speed by executing the combustion cycles.
This reduces the possibility that the engine speed achieved by the
combustion in each combustion cycle falls within the resonance
speed range. The resonance, which may occur in the powertrain unit
including the engine at the start of the engine, can be thus
reduced.
If the difference is larger than or equal to the reference value,
the fuel amount setting section sets the second injection amount so
that the engine speed achievable by combustion in one of the
combustion cycles, the engine speed of which combustion cycle has
been obtained to have the difference, is lower than the lower limit
of the resonance speed range, and so that the difference becomes
smaller than the reference value.
In this system for controlling start of the engine, if the engine
speed after start of the combustion cycles is lower than and
relatively far from the lower limit of the resonance speed range,
the second injection amount is set such that the engine speed
approaches the lower limit of the resonance speed range, up to a
predetermined range in which the amount of fuel to be injected is
set to the first injection amount. As a result, the engine speed
which has been relatively far from the lower limit of the resonance
speed range can efficiently approach the lower limit in a smaller
number of combustion cycles. This is thus advantages in rapid
ending of the start of the engine.
The engine may be a 4-cylinder, 4-cycle engine. In this case, the
speed obtaining section may detect a rotation speed of a crankshaft
when a cylinder executing an n-th combustion cycle is in a first
half of a compression stroke of the combustion cycle, and may
obtain the engine speed achieved by combustion in an (n-1)-th
combustion cycle based on the rotation speed of the crankshaft,
where n is a positive integer.
The "first half of a compression stroke" used herein corresponds to
the first half of a compression stroke when the compression stroke
is divided into the first and second halves. Note that the number
of the "combustion cycles" used herein is not counted up
independently for each cylinder, but is counted up for all the four
cylinders together. Specifically, in a 4-cylinder, 4-cycle engine,
the number of combustion cycles is incremented by one every time
the crankshaft turns 180 degrees.
In a 4-cylinder, 4-cycle engine, when combustion is performed in
the (n-1)-th combustion cycle, that is, when the cylinder executing
the (n-1)-th combustion cycle is in an expansion stroke, the
cylinder executing the n-th combustion cycle is in a compression
stroke. Thus, the engine speed achievable by the combustion in the
(n-1)-th combustion cycle can be obtained by detecting the rotation
speed of the crankshaft when the cylinder executing the n-th
combustion cycle is in the compression stroke. In particular, by
obtaining the engine speed in the first half of the compression
stroke, the information of the engine speed achieved by the
combustion in the (n-1)-th combustion cycle can be reflected in the
setting of the amount of fuel to be injected in the n-th combustion
cycle, and further in a control operation of the fuel
injection.
The engine may be a compression ignition engine which ignites fuel
fed into the combustion chamber by a compression operation of a
piston.
The "compression ignition engine" used herein includes a diesel
engine and a compression ignition gasoline engine. The "combustion
chamber" used herein is not limited to a space defined when the
piston reaches a compression top dead center. The term "combustion
chamber" is used in a broad sense.
A compression ignition engine including a diesel engine has a
compression ratio higher than the compression ratio of a general
spark ignition engine. Thus, the torque of such a compression
ignition engine varies relatively significantly, which causes
relatively significant vibrations in the engine at combustion in
each combustion cycle. If the engine speed achieved by combustion
in each combustion cycle falls within the resonance speed range
causing resonance in the powertrain, the vibrations caused by the
resonance in the powertrain and the vibrations caused by the torque
variations at that time together increase the vibrations generated
in the powertrain. The system for controlling start of the engine
according to the technique disclosed herein can reduce the
vibrations of the vehicle caused by the resonance in the
powertrain, and is thus particularly suitable for such a
compression ignition engine.
The system for controlling start of the engine may further include:
an airflow sensor which detects a flow rate of intake air flowing
through an intake passage provided in the engine; and a water
temperature sensor which is attached to the engine, and detects a
temperature of engine cooling water. In this case, the controller
may obtain an amount of intake air to be introduced to the
combustion chamber based on a detection signal of the airflow
sensor, and may obtain a temperature inside the combustion chamber
based on a detection signal of the water temperature sensor. If the
difference is smaller than the reference value, the fuel amount
setting section may set the first injection amount so as to allow
the engine to output a maximum torque corresponding to the amount
of intake air to be introduced to the combustion chamber and the
temperature inside the combustion chamber.
If the difference between the engine speed and the lower limit of
the resonance speed range is smaller than the reference value, that
is, if the engine speed is relatively close to the lower limit of
the resonance speed range, the first injection amount is set such
that the engine outputs the maximum torque. As a result, the engine
speed increases at a maximum rate due to the maximum torque
obtained by combustion in accordance with the first injection
amount. This allows the engine speed achieved by the combustion at
this moment to jump over the resonance speed range and fall out of
the resonance speed range.
If the difference is smaller than the reference value, the fuel
amount setting section may set the first injection amount such that
the engine speed increases at a maximum rate by combustion of the
combustion cycles in a start period from start of the combustion
cycles until the engine speed reaches the idle speed.
If the difference between the engine speed and the lower limit of
the resonance speed range is smaller than the reference value, that
is, if the engine speed is relatively close to the lower limit of
the resonance speed range, the first injection amount is set such
that the engine speed increases at a maximum rate in the start
period. As a result, the engine speed increases as significantly as
possible due to the torque obtained by the comparison according to
the first injection amount. This allows the engine speed achieved
by the combustion at this moment to jump over the resonance speed
range and fall out of the resonance speed range.
Advantages of the Invention
The method of and the system for controlling start of an engine
reduce vibrations generated in the powertrain unit including the
engine at starting the engine. This results in an advantageous
reduction in vibrations of the vehicle, which is caused by the
vibrations of the powertrain unit, and accompanying noise.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a diagram illustrating a rear view of a front part of a
vehicle including a compression ignition engine.
FIG. 2 is a diagram illustrating a configuration of the compression
ignition engine.
FIG. 3 is a diagram illustrating a block diagram associated with
control of the compression ignition engine.
FIG. 4 is a flowchart illustrating a process of controlling an
injector.
FIG. 5 is a diagram illustrating a configuration of a PCM.
FIG. 6 is a diagram for explaining a method of obtaining an engine
speed.
FIG. 7 is a diagram for explaining the method of obtaining the
engine speed.
FIG. 8 is a flowchart illustrating a process of setting the fuel
injection amount.
FIG. 9 is a diagram illustrating changes in the engine speed and
the fuel injection amount at start of the engine.
FIG. 10 is a diagram illustrating variations in a torque according
to the engine speed at start of the engine.
FIG. 11 is a diagram illustrating changes in the fuel injection
amount according to the difference between the engine speed and an
upper limit of a resonance speed range.
DESCRIPTION OF EMBODIMENTS
An exemplary embodiment will now be described in detail with
reference to the drawings. In the embodiment, the method of and the
system for controlling start of an engine will be described using a
compression ignition engine as an example.
FIG. 1 is a diagram illustrating a rear view of a front part of a
vehicle V including a compression ignition engine 1. As shown in
FIG. 1, the compression ignition engine (hereinafter simply
referred to as an "engine") 1 according to this embodiment is
mounted in a front-engine, front-drive, four-wheel vehicle
(hereinafter referred to as a "vehicle") V. The engine 1 forms the
powertrain PT of the vehicle V.
(Configuration of Powertrain)
The powertrain PT includes the engine 1 and a transmission 2. The
powertrain PT changes, in the transmission 2, the speed of the
output of the engine 1, and transmits the output having the changed
speed to front wheels 201 of the vehicle V.
The vehicle body of the vehicle V includes a plurality of frames.
For example, a pair of right and left front side frames 202
extending in the longitudinal direction of the vehicle V are
disposed at both ends of the powertrain PT in the vehicle width
direction. A subframe 203 is bridged below the front side frames
202 in the vehicle width direction.
The powertrain PT according to this embodiment employs a pendulum
support structure. Specifically, the upper parts of both ends of
the powertrain PT in the vehicle width direction (namely, parts of
the powertrain PT located above the center of gravity G) are
supported by the front side frames 202 via respective engine mounts
204. The engine mounts 204 have elastic force, and support and
suspend both the ends of the powertrain PT.
In the case of employing the pendulum type, the powertrain PT
vibrates so as to rotate about a roll axis A extending
substantially in the vehicle width direction, using torque
variations at the time, for example, when the engine 1 operates as
vibration force. In order to reduce such vibrations, the lower part
of the powertrain PT (namely, part of the powertrain PT located
below the center of gravity G) is coupled to the subframe 203 via a
torque rod 205.
Note that the resonance frequency at the time when the powertrain
PT vibrates is determined depending on the hardware structure or
the support structure of the powertrain PT. Although not described
in detail, the resonance frequency according to this embodiment is
adjusted so that the engine speed corresponding to the resonance
frequency (hereinafter referred to as a "resonance speed") Rr is at
least lower than an idle speed Ri of the engine 1. The idle speed
Ri is set so as not to cause engine stall, for example, when the
vehicle V does not travel and when the accelerator pedal is not
depressed.
(General Configuration of Engine)
FIG. 2 illustrates a configuration of the engine 1. FIG. 3 is a
block diagram associated with control of the engine 1. The engine 1
is an inline 4-cylinder, 4-cycle diesel engine configured to ignite
fuel, fed into a combustion chamber, by compression operation of
pistons. However, the engine 1 is not limited to a diesel engine.
The technique disclosed herein is applicable to, for example, a
compression ignition gasoline engine.
As shown in FIG. 2, the engine 1 includes a cylinder block 11
provided with four cylinders 11a (only one is shown), a cylinder
head 12 located above the cylinder block 11, and an oil pan 13
located below the cylinder block 11 and storing lubricant. A piston
14 is slidably fitted into each of the cylinders 11a. The top
surface of the piston 14 has a cavity defining a combustion chamber
14a.
The piston 14 is coupled to a crankshaft 15 via a connecting rod
14b. The crankshaft 15 is coupled to the transmission 2 described
above. A trigger plate 92 is attached to the crankshaft 15. The
trigger plate 92 rotates integrally with the crankshaft 15.
Note that the "combustion chamber" used herein is not limited to a
space defined when the piston 14 reaches a compression top dead
center. The term "combustion chamber" is used in a broad sense.
That is, the "combustion chamber" may denote the space defined by
the piston 14, the cylinder 11a, and the cylinder head 12,
regardless of the position of the piston 14.
The geometric compression ratio of the engine 1 is set higher than
that of a general spark ignition engine. Specifically, the
geometric compression ratio of the engine 1 is set to 14 or higher.
This setting is a mere example, and may be changed as
appropriate.
The cylinder block 11 includes a starter motor 91 (shown only in
FIG. 3) for starting cranking at start of the engine 1. The starter
motor 91 detachably meshes with a ring gear (not shown), which is
coupled to an end portion of the crankshaft 15. To start cranking
at the start of the engine 1, the starter motor 91 is driven. The
starter motor 91 meshes with the ring gear to transmit power of the
starter motor 91 to the ring gear, thereby rotating and driving the
crankshaft 15.
The cylinder head 12 includes two intake ports 16 and two exhaust
ports 17 for each cylinder 11a. Both the intake ports 16 and the
exhaust ports 17 communicate with the corresponding one of the
combustion chambers 14a. Each intake port 16 is provided with an
intake valve 21 for opening and closing an opening at the
combustion chamber 14a. Similarly, each exhaust port 17 is provided
with an exhaust valve 22 for opening and closing an opening at the
combustion chamber 14a.
An injector 18 for each cylinder 11a is attached to the cylinder
head 12. The injector 18 directly injects fuel into the cylinder
11a, thereby feeding the fuel into corresponding one of the
combustion chambers 14a. The fuel is fed to the injector 18 from a
fuel tank 52 via a fuel feeding system 51. This fuel feeding system
51 includes a low-pressure electric fuel pump (not shown) provided
inside the fuel tank 52, a fuel filter 53, a high-pressure fuel
pump 54, and a common rail 55.
The high-pressure fuel pump 54 is driven by a rotating member (e.g.
a camshaft) of the engine 1. This high-pressure fuel pump 54 pumps
low-pressure fuel, which has been fed from the fuel tank 52 via the
low-pressure fuel pump and the fuel filter 53, to the common rail
55 at a high pressure. The common rail 55 stores the pumped fuel at
a high pressure. The fuel stored in the common rail 55 is injected
from the injector 18 into the combustion chamber 14a by operation
of the injector 18.
Note that the excessive fuel generated in the low-pressure fuel
pump, the high-pressure fuel pump 54, and the common rail 55, and
the injector 18 returns via a return passage 56 (directly in the
case of the excessive fuel generated in the low-pressure fuel pump)
to the fuel tank 52. The configuration of the fuel feeding system
51 is not limited thereto.
The cylinder head 12 includes a glow plug 19 for each cylinder 11a.
The glow plug 19 warms gas which has been sucked into the cylinder
11a at cold start of the engine 1 to improve fuel
ignitionability.
An intake passage 30 is connected to one side surface of the engine
1. The gas to be introduced into the combustion chambers 14a flows
through the intake passage 30. On the other hand, an exhaust
passage 40 is connected to the other side surface of the engine 1.
The exhaust gas discharged from the combustion chambers 14a flows
through the exhaust passage 40. The intake and exhaust passages 30
and 40 are provided with a turbo supercharger 61 that supercharges
gas.
Specifically, the intake passage 30 communicates with the intake
ports 16 of each cylinder 11a. An air cleaner 31 filtering fresh
air is provided at the upstream end of the intake passage 30. A
surge tank 34 is provided near the downstream end of the intake
passage 30. Although not shown in detail, a portion of the intake
passage 30 downstream of the surge tank 34 serves as independent
passages, each branches off to one of the cylinders 11a. Each of
the independent passages has a downstream end connected to the
intake ports 16 of the corresponding one of the cylinders 11a.
In the intake passage 30 between the air cleaner 31 and the surge
tank 34, a compressor 61a of the turbo supercharger 61, an intake
shutter valve 36, and an intercooler 35 are arranged sequentially
from the upstream side. The intercooler 35 cools the gas compressed
by the compressor 61a. The intake shutter valve 36 is basically
fully open. The intercooler 35 is configured to cool the gas using
cooling water fed by an electric water pump 37.
On the other hand, the exhaust passage 40 communicates with the
exhaust ports 17 of each cylinder 11a. Specifically, although not
shown in detail, an upstream portion of the exhaust passage 40
serves as independent passages, each branches off to one of the
cylinders 11a. Each of the independent passages has an upstream end
connected to the exhaust ports 17 of the corresponding one of the
cylinders 11a. A portion of the exhaust passage 40 downstream of
the independent passages serves as a collector, into which the
independent passages converge.
In portions of the exhaust passage 40 downstream of the collector,
a turbine 61b of the turbo supercharger 61, an exhaust gas purifier
41, and a silencer 42 are disposed sequentially from the upstream
side. The exhaust gas purifier 41 purifies harmful components in
the exhaust gas of the engine 1. The exhaust gas purifier 41
includes an oxidation catalyst 41a and a diesel particulate filter
(hereinafter referred to as a "DPF") 41b sequentially from the
upstream side.
The oxidation catalyst 41a includes an oxidation catalyst which
supports platinum, a mixture of platinum and palladium, or any
other component, and promotes reactions in which CO and HC in the
exhaust gas are oxidized to generate CO.sub.2 and H.sub.2O. On the
other hand, the DPF 41b traps and collects fine particles such as
soot contained in the exhaust gas of the engine 1. The DPF 41b may
be coated with an oxidation catalyst.
The turbo supercharger 61 includes, as described above, the
compressor 61a disposed in the intake passage 30, and the turbine
61b disposed in the exhaust passage 40. The turbine 61b is rotated
by the flow of the exhaust gas. The compressor 61a is coupled to
the turbine 61b, and operates in accordance with the rotation of
the turbine 61b. Once the compressor 61a operates, the turbo
supercharger 61 compresses the gas to be introduced into the
combustion chambers 14a. A VGT throttle valve 62 is provided near
the upstream side of the turbine 61b in the exhaust passage 40. The
opening degree (i.e. throttling) of the VGT throttle valve 62 is
controlled to adjust the flow speed of the exhaust gas to be
transmitted to the turbine 61b.
The engine 1 causes part of the exhaust gas to flow back to the
intake passage 30 from the exhaust passage 40. To realize the
backflow of the exhaust gas, a high-pressure EGR passage 71 and a
low-pressure EGR passage 81 are provided.
The high-pressure EGR passage 71 connects a portion of the exhaust
passage 40 between the collector and the turbine 61b of the turbo
supercharger 61 (i.e., a portion upstream of the turbine 61b of the
turbo supercharger 61) to a portion of the intake passage 30
between the surge tank 34 and the intercooler 35 (i.e., a portion
downstream of the compressor 61a of the turbo supercharger 61). In
the high-pressure EGR passage 71, a high-pressure EGR valve 73 is
disposed, which adjusts the backflow rate of the exhaust gas
through the high-pressure EGR passage 71.
The low-pressure EGR passage 81 connects a portion of the exhaust
passage 40 between the exhaust gas purifier 41 and the silencer 42
(i.e., a portion downstream of the turbine 61b of the turbo
supercharger 61) to a portion of the intake passage 30 between the
compressor 61a of the turbo supercharger 61 and the air cleaner 31
(i.e., a portion upstream of the compressor 61a of the turbo
supercharger 61). In the low-pressure EGR passage 81, a
low-pressure EGR cooler 82 and a low-pressure EGR valve 83 are
disposed. The low-pressure EGR cooler 82 cools the exhaust gas
passing through the low-pressure EGR passage 81. The low-pressure
EGR valve 83 adjusts the backflow rate of the exhaust gas through
the low-pressure EGR passage 81.
The compression ignition engine includes a powertrain control
module (PCM) 100 shown in FIG. 3 to control the entire powertrain
PT including the engine 1. The PCM 100 is a controller including a
known microcomputer as a base element. The PCM 100 also includes a
central processing unit (CPU), a memory such as a random access
memory (RAM) and a read only memory (ROM), and an input and output
(I/O) bus. The CPU executes programs. The memory stores programs
and data. The I/O bus inputs and outputs electrical signals. The
PCM 100 is a mere example of a "controller."
As shown in FIGS. 2 and 3, various types of sensors SW1 to SW11 are
connected to the PCM 100. The sensors SW1 to SW11 output respective
detection signals to the PCM 100. The sensors SW1 to SW11 include
the following sensors.
Specifically, an airflow sensor SW2 is located downstream of the
air cleaner 31 in the intake passage 30, and detects the flow rate
of fresh air (or air) flowing through the intake passage 30. An
intake air temperature sensor SW3 detects the temperature of the
fresh air. An intake air pressure sensor SW5 is located downstream
of the intercooler 35, and detects the pressure of the gas which
has passed through the intercooler 35. An intake gas temperature
sensor SW4 is attached to the surge tank 34, and detects the
temperature of the gas to be fed into the cylinders 11a. A water
temperature sensor SW8 is attached to the engine 1, and detects the
temperature of engine cooling water (hereinafter referred to as a
"cooling water temperature"). A crank angle sensor SW1 detects the
rotation angle of the crankshaft 15. An exhaust gas pressure sensor
SW6 is provided near a connecting portion of the exhaust passage 40
with the high-pressure EGR passage 71, and detects the pressure of
the exhaust gas exhausted from the combustion chambers 14a. A DPF
differential pressure sensor SW11 detects the differential pressure
of the exhaust gas before and after passing through the DPF 41b. An
exhaust gas temperature sensor SW7 detects the temperature of the
exhaust gas after passing through the DPF 41b. An accelerator
position sensor SW9 detects the accelerator position corresponding
to the amount of depression of the accelerator pedal. A vehicle
speed sensor SW10 detects the rotation speed of the output shaft of
the transmission 2. The crank angle sensor SW1 used herein is an
example of an "engine speed sensor."
The PCM 100 determines the operating state of the engine 1 and the
traveling state of the vehicle V based on detection signals of
these sensors, and calculates control variables of each actuator
according to the operating state of the engine 1 and the traveling
state of the vehicle V. The PCM 100 outputs the control signals
associated with the obtained control variables, for example, to the
injector 18, the intake shutter valve 36, the electric water pump
37, an exhaust shutter valve 43, the high-pressure fuel pump 54,
the VGT throttle valve 62, the high-pressure EGR valve 73, the
low-pressure EGR valve 83, and the starter motor 91.
Among the functions of this PCM 100, the start control functions
for the engine 1 will be particularly described below in detail.
FIG. 5 is a diagram illustrating a configuration of the PCM
100.
As shown in FIG. 5, the PCM 100 includes the following as
functional elements associated with the start control of the engine
1. An engine starter 101 starts cranking using the starter motor
91. A speed obtaining section 102 obtains the engine speed. A
cooling water temperature obtaining section 103 obtains the
temperature of the engine cooling water. An in-cylinder temperature
obtaining section 104 obtains the temperature inside the combustion
chambers 14a (hereinafter referred to as an "in-cylinder
temperature") based on the water temperature. An intake air amount
obtaining section 105 obtains the amount of intake air to be
introduced into the combustion chambers 14a. An injection amount
setting section 106 sets the fuel injection amount injected by the
injectors 18 based on the engine speed, the in-cylinder
temperature, and the amount of intake air.
When the engine 1 starts, the engine starter 101 inputs a control
signal to the starter motor 91. Once the control signal is input
from the engine starter 101, the starter motor 91 rotates and
drives the crankshaft 15. This rotation starts cranking of the
engine 1.
The speed obtaining section 102 detects or estimates the engine
speed based on the detection signal of the crank angle sensor SW1,
and outputs a signal corresponding to the detected or estimated
value to the injection amount setting section 106.
Specifically, when the starter motor 91 performs cranking, the
speed obtaining section 102 detects or estimates the engine speed
at a predetermined timing. In the idle operation of the engine 1
and the normal operation of the engine 1 (while the vehicle V
travels), the speed obtaining section 102 obtains, prior to fuel
injection in the (n+1)-th combustion cycle, an engine speed which
can be achieved by combustion in a cycle before the (n+1)-th
combustion cycle (i.e., combustion at or prior to an n-th cycle),
where n is a positive integer, for example. The speed obtaining
section 102 also generates a signal corresponding to the obtained
engine speed, and outputs the signal to the injection amount
setting section 106.
Note that the number of the "combustion cycles" used herein is not
counted up independently for each cylinder, but is counted up for
all the four cylinders together. Specifically, in a 4-cylinder
engine, the combustion cycles are offset by 180 degrees. Thus, in
view of the fact that one cycle ends in each cylinder 11a every
time the crankshaft 15 turns 720 degrees, the number of the cycles
is incremented by one every time the crankshaft 15 turns 180
degrees.
FIGS. 6 and 7 are diagrams for explaining a method of obtaining the
engine speed. The four cylinders 11a shown in FIG. 6 may be
hereinafter referred to as a first cylinder (#1), a second cylinder
(#2), a third cylinder (#3), and a fourth cylinder (#4) arranged
sequentially along the cylinder bank. That is, in the engine 1,
combustion occurs sequentially in the #1, #3, #4, and #2 every time
the crankshaft 15 turns 720 degrees. As shown in FIG. 6, the number
of the combustion cycles is incremented by one every time a series
of strokes, namely, intake, compression, expansion, and exhaust
strokes, is performed in one of the cylinders 11a.
As shown in FIG. 7, the speed obtaining section 102 obtains, in the
idle and normal operations, the engine speed based on the times
(t1+t2+t3+t4+t5+t6 shown in FIGS. 6 and 7) required by the trigger
plate 92 to turn 180 degrees in one of the cylinders 11a (e.g., the
fourth cylinder (#4)) which is to perform combustion in the n-th
combustion cycle, from the first half of the intake stroke through
the intake bottom dead center to the first half of the compression
stroke. As shown in FIG. 7, ti, where i is an integer from 1 to 6,
represents time required by the trigger plate 92 to turn 30 degrees
(hereinafter referred to as a "unit of rotation time").
In the example of FIGS. 6 and 7, the speed obtaining section 102
calculates the average of six units (t1+t2+ . . . +t6) of rotation
time, obtains the rotation speed of the trigger plate 92 (i.e., the
crankshaft 15) based on the average, and obtains the engine speed
based on the rotation speed of the trigger plate 92. In the normal
operation, the trigger plate 92 rotates at a higher speed than in
the start of the engine. Thus, the engine speed can be detected
more accurately by taking into account the units of rotation time
in the intake stroke, and reflecting the influence of variations in
the engine speed due to combustion of each combustion cycle, than
in the case where only the units of rotation time in each
compression stroke are taken into account. This method of obtaining
the engine speed is advantageous in securing high accuracy in
detecting the engine speed in the normal operation.
However, at the start of the engine 1, variations in the engine
speed due to combustion of each combustion cycle are relatively
large, compared to the time when the engine 1 operates at a speed
higher than the idle speed, because there is a great influence of
the inertia of the flywheel. Thus, if the length of time required
for a half rotation of the trigger plate 92 (i.e., six units of
rotation time) is used to obtain the engine speed, the accuracy in
detecting the engine speed rather deteriorates. For this reason,
the above-described method of obtaining the engine speed in the
normal operation is not suitable as a method of obtaining the
engine speed achieved by the combustion in the previous (n-1)-th
combustion cycle, before the setting of the fuel injection amount
in the n-th combustion cycle at the start of the engine.
To address this problem, the speed obtaining section 102 obtains
the engine speed based on the unit (t1 in FIGS. 6 and 7) of
rotation time in the first half of the compression stroke, in a
period after the engine 1 starts combustion cycles until the engine
speed reaches a predetermined idle speed (hereinafter referred to
as a "start period"). As shown in FIG. 6, the first half of the
compression stroke is the timing immediately before the start of
fuel injection, and when the speed variations caused by the
previous combustion converge.
In the engine 1, when combustion is performed in the (n-1)-th
combustion cycle, that is, when the cylinder 11a executing this
combustion cycle is in an expansion stroke, the cylinder 11a
executing the n-th combustion cycle is in a compression stroke.
Thus, the engine speed achievable by the combustion in the (n-1)-th
combustion cycle can be obtained by detecting the rotation speed of
the crankshaft 15 when the cylinder 11a executing the n-th
combustion cycle is in the compression stroke. In particular, by
obtaining the engine speed in the first half of the compression
stroke, the information of the engine speed achieved by the
combustion in the (n-1)-th combustion cycle can be reflected in the
setting of the torque in the n-th combustion cycle, and further in
a control operation of the manipulation according to the
torque.
In this manner, the speed obtaining section 102 obtains, before
performing fuel injection in the n-th combustion cycle, the engine
speed (hereinafter may be referred to as a "present engine speed")
achieved by the combustion in the previous (n-1)-th combustion
cycle. Then, the speed obtaining section 102 generates a signal
corresponding to the present engine speed, and outputs the signal
to the injection amount setting section 106.
The cooling water temperature obtaining section 103 detects the
temperature of the engine cooling water based on the detection
signal of the water temperature sensor SW8, and outputs a signal
corresponding to the detected value to the in-cylinder temperature
obtaining section 104.
The in-cylinder temperature obtaining section 104 detects or
estimates the in-cylinder temperature based on the value detected
by the cooling water temperature obtaining section 103, and outputs
a signal corresponding to the detected or estimated value to the
injection amount setting section 106.
The intake air amount obtaining section 105 detects or estimates
the amount of intake air to be introduced into the combustion
chambers 14a of the cylinders 11a based on the detection signal of
the airflow sensor SW2 and the detection signal of the intake air
temperature sensor SW3, and outputs a signal corresponding to the
detected or estimated value to the fuel amount setting section
106.
The injection amount setting section 106 sets, within the start
period described above, the amount of fuel injected by the
injectors 18 in the next and subsequent combustion cycles based on
the engine speed detected or estimated by the speed obtaining
section 102, the in-cylinder temperature detected or estimated by
the in-cylinder temperature obtaining section 104, the amount of
intake air detected or estimated by the intake air amount obtaining
section 105. In the engine 1, the torque varies depending on the
amount of injected fuel. The more fuel is injected, the larger
torque of the engine 1 is obtained, while the less fuel is
injected, the smaller torque of the engine 1 is obtained.
As described above, the resonance speed Rr causing resonance in the
powertrain PT is lower than the idle speed Ri. Thus, within the
start period, the engine speed at combustion in each combustion
cycle may fall at and around the resonance speed Rr causing
resonance in the powertrain PT. In this case, there is a fear that
the vibrations of the entire powertrain PT including the engine 1
may be excited and increased by the resonance.
To address this problem, the present inventors found the following
torque control which prevents the engine speed at combustion in
each combustion cycle from falling at and around the resonance
speed Rr through the processing of the injection amount setting
section 106, and which, even if the engine speed falls within the
range around the resonance speed Rr, can reduce vibrations
associated with the resonance as soon as possible.
The PCM 100 stores a resonance speed range Br which includes the
resonance speed Rr and a resonance speed range around the resonance
speed Rr, as an index for determining whether the engine speed
falls at and around the resonance speed Rr or not. The lower limit
R1 and the upper limit R2 of this resonance speed range Br are set
in advance as thresholds so that the acceleration caused when the
engine 1 vibrates, and eventually when the powertrain PT vibrates,
falls within a predetermined range. The lower limit R1 is higher
than a cranking determination value Rc. On the other hand, the
upper limit R2 is lower than the idle speed Ri.
(Control Associated with Fuel Injection)
FIG. 4 illustrates a control process associated with fuel
injection. The PCM 100 executes fuel injection using the injectors
18 in the process shown in FIG. 4 including the execution of the
injection amount setting section 106.
Once the process shown in FIG. 4 starts, the PCM 100 first obtains
various types of information in step S101, based on the detection
signals obtained from the sensors. For example, the PCM 100 obtains
the engine speed, the accelerator position, the temperature of
cooling water, and the amount of intake air. Then, in step S102,
the injection amount setting section 106 of the PCM 100 sets a
target amount of fuel to be injected into the combustion chambers
14a (hereinafter referred to as a "fuel injection amount") based on
the information obtained in step S101. Furthermore, in step S103,
the PCM 100 sets the injection pattern and injection timing at the
execution of fuel injection. After that, in step S104, the PCM 100
generates control signals corresponding to the settings in steps
S102 to S103, and inputs to the injectors 18.
In such a control process associated with fuel injection, step S101
is an example of a "step of obtaining an engine speed." Step S102
is an example of a "step of setting an amount of fuel" and a "step
of setting a torque." In the engine 1, the torque is adjusted
depending on the fuel injection amount described above. The more
fuel is injected, the larger torque is obtained, while the less
fuel is injected, the smaller torque is obtained. Setting the fuel
injection amount is equivalent to setting the torque of the engine
1.
(Process of Setting Fuel Injection Amount)
Of the start control of the engine 1, a process of setting the fuel
injection amount will be particularly described in detail below
with reference to FIG. 8. FIG. 8 is a flowchart illustrating the
process of setting the fuel injection amount. The process shown in
FIG. 8 is an example of processing according to step S102 of FIG.
6.
In the process shown in FIG. 8, the injection amount setting
section 106 sets the fuel injection amount to be smaller than or
equal to a predetermined maximum injection amount Fm. The maximum
injection amount Fm decreases when the in-cylinder temperature is
high, and increases when the in-cylinder temperature is low. The
maximum injection amount Fm is set so that the engine outputs the
maximum torque corresponding to the in-cylinder temperature and the
amount of intake air. The maximum injection amount Fm increases
when a larger amount of intake air is introduced, and decreases
when a smaller amount of intake air is introduced.
Once the process shown in FIG. 8 starts, the injection amount
setting section 106 first obtains the engine speed and determines
whether or not cranking has ended in step S201. This determination
is made based on whether or not the engine speed is higher than or
equal to the cranking determination value Rc illustrated in FIGS. 9
and 10. The cranking determination value Rc is set in advance in
accordance with, for example, the configuration of the engine
1.
In this step S201, if the engine speed is lower than the cranking
determination value Rc, the section determines that the cranking
has not ended and concludes NO. If the determination is NO, the
process proceeds to step S207. In step S207, the injection amount
setting section 106 sets the fuel injection amount to zero, and
continues cranking. On the other hand, in step S201, if the engine
speed reaches at or higher than a cranking turnover value Rc, the
section determines that the cranking has ended, and concludes YES.
If the determination is YES, the process proceeds from step S201 to
step S202 so that cranking shifts to combustion cycles
("firing").
In step S202, the injection amount setting section 106 determines
whether or not the difference between the lower limit R1 of the
resonance speed range Br and the engine speed is lower than a
predetermined reference value. Specifically, the present embodiment
employs a method of determining whether or not the engine speed is
higher than or equal to a predetermined determination threshold
value R0. The determination threshold value R0 is set in advance to
a value smaller than the lower limit R1 of the resonance speed
range Br by the predetermined reference value. The determination
threshold value R0 is greater than the cranking determination value
Rc, and smaller than the lower limit R1 of the resonance speed
range Br.
In step S202, the process proceeds to step S208 if the engine speed
is lower than the predetermined determination threshold value R0
(i.e., if the difference between the lower limit R1 of the
resonance speed range Br and the engine speed is smaller than the
reference value) and the determination is NO. In step S208, the
injection amount setting section 106 sets the fuel injection amount
to a predetermined step-over injection amount F1, and the process
goes to Return.
The step-over injection amount F1 is set such that when the fuel
injection with the step-over injection amount F1 is performed, the
engine speed achieved by the combustion associated with the fuel
injection is higher than or equal to the determination threshold
value R0 and lower than the lower limit R1 of the resonance speed
range Br. The step-over injection amount F1 is smaller than the
maximum injection amount Fm described above (i.e., step-over
injection amount<maximum injection amount). The step-over
injection amount F1 is an example of the "second injection amount"
for obtaining a "second torque."
On the other hand, in step S202, if the engine speed is higher than
or equal to the predetermined determination threshold value R0
(i.e., the difference between the lower limit R1 of the resonance
speed range Br and the engine speed is larger than or equal to the
reference value), and the determination is YES, the process
proceeds to step S203. In step S203, the injection amount setting
section 106 determines whether or not the engine speed is higher
than or equal to the lower limit R1 of the resonance speed range
Br.
In step S203, the process proceeds to step S209 if the engine speed
is lower than the lower limit R1 of the resonance speed range Br
and the determination is NO. In step S209, the injection amount
setting section 106 sets the fuel injection amount to a
predetermined jump-over injection amount F2, and the process goes
to Return. On the other hand, in step S203, if the engine speed is
higher than or equal to the lower limit R1 of the resonance speed
range Br and the determination is YES, the process proceeds to step
S204.
The jump-over injection amount F2 set in step S209 as the fuel
injection amount is equal to the maximum injection amount Fm
described above (i.e., jump-over injection amount=maximum injection
amount). Thus, the jump-over injection amount F2 is larger than the
step-over injection amount F1 described above (jump-over injection
amount>step-over injection amount). The jump-over injection
amount F2 is set such that the engine speed increases at a maximum
rate by the combustion in the combustion cycles in the start period
from the start of combustion cycles until the engine speed reaches
the idle speed.
If the fuel injection amount is set to the jump-over injection
amount F2, the engine speed is increased more by an increased
amount of the fuel injected, than in the case, for example, where
the fuel injection amount is set to the step-over injection amount
F1. This is advantageous in increasing the engine speed, by the
combustion in one cycle, from a value smaller than the lower limit
R1 of the resonance speed range Br to a value greater than the
upper limit R2 (hereinafter referred to as "jumping over the
resonance speed range Br"). The jump-over injection amount F2 is an
example of the "first injection amount" for obtaining a "first
torque."
Even if the maximum injection amount Fm is set as the jump-over
injection amount F2 as in step S203, the engine speed does not
always jump over the resonance speed range Br successfully. For
example, the maximum injection amount Fm increases and decreases in
accordance with the in-cylinder temperature. Furthermore,
in-cylinder oxygen concentration varies due to changes in the air
density which varies according to changes in the intake air
temperature. The obtainable torque therefore changes even if the
same amount of fuel is injected. In addition, the resonance speed
range Br may change in accordance with the external environment.
Specifically, elastic properties of the engine mount 204 change
with a decrease in the outside air temperature. As a result, the
acceleration at the time when the powertrain PT vibrates changes,
and hence the lower limit R1 and the upper limit R2 of the
resonance speed range Br also change. Because of such
circumstances, the engine speed at combustion in each combustion
cycle may fall within the resonance speed range Br.
To address this problem, when the engine speed falls within the
resonance speed range Br, the injection amount setting section 106
according to this embodiment executes, in steps S204 and S210,
processing for immediately reducing vibrations caused by such
engine speed.
In step S204, the section determines whether or not the engine
speed is higher than or equal to the upper limit R2 of the
resonance speed range Br. In step S204, the process proceeds to
step S210 if the engine speed is lower than the upper limit R2 of
the resonance speed range Br and the determination is NO. In step
S210, the injection amount setting section 106 sets the fuel
injection amount to the predetermined jump-over injection amount
F2, and the process goes to Return. On the other hand, in step
S204, if the engine speed is higher than or equal to the upper
limit R2 of the resonance speed range Br and the determination is
YES, the process proceeds to step S205.
In step S210, if the fuel injection amount is set to the jump-over
injection amount F2, the engine speed increases significantly as in
the processing in step S209 described above. This is advantages in
increasing the engine speed from a value within the resonance speed
range Br to a value greater than or equal to the upper limit R2 of
the resonance speed range Br (hereinafter referred to as "getting
out of the resonance speed range Br").
Note that, in step S204, the jump-over injection amount F2 that is
set as the fuel injection amount is not necessarily equal to the
maximum injection amount Fm. The jump-over injection amount F2 may
be at least larger than the fuel injection amount that is set when
the engine speed is higher than or equal to the upper limit R2 of
the resonance speed range Br. Specifically, the jump-over injection
amount F2 may be larger than the fuel injection amount that is set
for the combustion cycle subsequent to the combustion cycle in
which the engine speed has successfully jumped over the resonance
speed range Br, or larger than the fuel injection amount that is
set for the combustion cycle subsequent to the combustion cycle in
which the engine speed has gotten out of the resonance speed range
Br.
Even if the engine speed successfully jumps over or gets out of the
resonance speed range Br, torque variations may induce resonance
immediately after the engine speed has passed through the resonance
speed range Br.
To address this problem, when the engine speed successfully jumps
over or gets out of the resonance speed range Br, the injection
amount setting section 106 according to this embodiment executes,
in steps S205 and S211, processing of reducing the induction of
resonance after the engine speed have passed through the resonance
speed range Br.
In step S205, the injection amount setting section 106 determines
whether or not the engine speed is higher than or equal to the idle
speed Ri. In step S205, if the engine speed is lower than the idle
speed Ri, and the determination is NO, that is, the engine speed
successfully jumps over or gets out of the resonance speed range Br
but fails to reach the idle operating state, the process proceeds
to step S211. On the other hand, in step S205, if the engine speed
is higher than or equal to the idle speed Ri, and the determination
is YES, the process proceeds to step S206. In step S206, the
injection amount setting section 106 sets the fuel injection amount
to an amount Fi corresponding to the idle operation, and the
process goes to Return, thereby starting the idle operation.
In step S211, the injection amount setting section 106 sets the
fuel injection amount in the subsequent combustion cycle to a
predetermined resonance induction reducing amount F3, and the
process goes to Return. The resonance induction reducing amount F3
is at least smaller than the jump-over injection amount F2 that is
set so as to jump over the resonance speed range Br (i.e.,
resonance induction reducing amount<jump-over injection amount).
This is advantages in reducing induction of the resonance, since
the torque variations decrease by an amount of decrease in the
resonance induction reducing amount F3.
The injection amount setting section 106 calculates the difference
.DELTA.R between the engine speed achieved in the combustion cycles
at a time subsequent to when the engine speed has passed through
the resonance speed range Br (specifically, in the combustion
cycles at a time subsequent to when the engine speed has jumped
over or gotten out of the resonance speed range Br) and the upper
limit R2 of the resonance speed range Br. The section also sets the
resonance induction reducing amount F3 to be smaller if the
difference .DELTA.R is small, than if the difference .DELTA.R is
large.
That is, the resonance induction reducing amount F3 is set not only
in the combustion cycle immediately after the engine speed has
jumped over or gotten out of the resonance speed range Br, but also
until the engine speed reaches the idle operating state.
FIG. 11 illustrates the fuel injection amount (i.e., the resonance
induction reducing amount F3) at a time subsequent to when the
engine speed has passed through the resonance speed range Br. As
shown in FIG. 11, when the difference .DELTA.R increases from zero
to a predetermined resonance induction determination value Rt, the
resonance induction reducing amount F3 increases with an increase
in the difference .DELTA.R, and reaches the maximum injection
amount Fm. As the resonance induction reducing amount F3 increases,
the torque generated by the combustion based on the resonance
induction reducing amount F3 also increases along the straight line
L of FIG. 11. The straight line L is defined based on the vibration
characteristics of the powertrain PT. It is defined that
acceleration caused by the vibrations of the powertrain PT exceeds
a tolerance range when the torque generated by the operation of the
engine 1 exceeds the straight line L. Setting the fuel injection
amount in accordance with the characteristics shown in FIG. 11
causes the engine 1 to output torque having a value along the
straight line L, and thus allows the acceleration to fall within
the tolerance range.
On the other hand, if the difference .DELTA.R is larger than the
resonance induction determination value Rt, the resonance induction
reducing amount F3 is constant at the maximum injection amount
Fm.
Now, how the engine speed increases when the start of the engine 1
is controlled in accordance with the above-described process of
setting the fuel injection amount, will be described below with
reference to FIGS. 9 and 10 using examples.
FIG. 9 is a time chart illustrating changes in the engine speed and
changes in the fuel injection amount at start of the engine 1. FIG.
10 illustrates variations in the torque with respect to the engine
speed at the start of the engine 1. Ta1 to Ta5 and Tb1 to Tb6 in
FIGS. 9 and 10 represent states achieved by combustion in the
combustion cycles.
First, a first example will be described, in which the engine speed
at the time when it is determined that cranking has ended in step
S201 is higher than the determination threshold value R0. In the
first example, the engine speed follows the rising path formed by
connecting the white circles (o) shown in the uppermost graph in
FIG. 9. As shown in the middle graph, the fuel injection amounts in
the respective combustion cycles are set immediately before the
combustion times Ta1 to Ta5. In FIG. 10, the relationship between
the engine speed and the torque shifts from Ta1 through Ta2, Ta3,
and Ta4 to Ta5 in accordance with combustion in the cycles.
Specifically, in the first example, the engine speed at the time
when the cranking has ended is higher than or equal to the
determination threshold value R0 and lower than the lower limit R1
of the resonance speed range Br. Thus, the fuel injection amount in
the first combustion cycle is set to the jump-over injection amount
F2 by the fuel amount setting section 106 (in step S209). When the
set amount of fuel is injected, and the injected fuel is burnt, the
engine speed is increased more significantly compared to when the
cranking has ended, due to the torque obtained by the combustion.
The engine speed jumps over the resonance speed range Br in this
manner.
When the engine speed jumps over the resonance speed range Br, the
engine speed achieved by the combustion in the first cycle (i.e.
the first ignition) increases, as indicated by the solid line
connecting Ta1 and Ta2 shown in FIGS. 9 and 10, to a speed higher
than the upper limit R2 of the resonance speed range Br and lower
than the idle speed Ri. Thus, the fuel injection amount in the
second combustion cycle is set to the resonance induction reducing
amount F3, which is smaller than the jump-over injection amount F2,
by the fuel amount setting section 106 (in step S211). When the set
amount of fuel is injected, and the injected fuel is burnt, the
engine speed is increased less significantly due to the torque
obtained by the combustion, by the reduced amount of the fuel
injection, compared to when the first combustion cycle is
performed.
When combustion is performed in the second combustion cycle, the
engine speed obtained by the combustion increases as indicated by
the solid line connecting Ta2 to Ta3 shown in FIGS. 9 and 10, but
is still lower than the idle speed Ri. Thus, the fuel injection
amount in the third cycle is also set to the resonance induction
reducing amount F3 by the fuel setting section 106 (in step S211).
Since the engine speed increases to be relatively far from the
resonance speed range Br, the resonance induction reducing amount
in the third cycle is set to be larger than the resonance induction
reducing amount F3 set in the second combustion cycle. When the set
amount of fuel is injected, and the injected fuel is burnt, the
engine speed is increased more significantly due to the torque
obtained by the combustion, by the increased amount of the fuel
injection, compared to when the second combustion cycle is
performed.
When combustion is performed in the third combustion cycle, the
engine speed achieved by the combustion increases as indicated by
the solid line connecting Ta3 to Ta4 shown in FIGS. 9 and 10, and
the engine speed becomes higher than the idle speed Ri. Thus, the
fuel injection amount in the fourth combustion cycle is set to the
amount Fi corresponding to the idle operation by the fuel amount
setting section 106 (in step S206). When the set amount of fuel is
injected and the injected fuel is burnt, the engine speed is
maintained at the speed higher than or equal to the idle speed Ri,
due to the torque obtained by the combustion, thereby performing
the idle operation.
Now, a second example will be described, in which the engine speed
at the time when the cranking has ended is lower than the
determination threshold value R0. In the second example, the engine
speed follows the rising path formed by connecting the black
circles (.circle-solid.) shown in the uppermost graph in FIG. 9. As
shown in the lowermost graph, the fuel injection amounts in the
respective combustion cycles are set immediately before the
combustion times Tb1 to Tb5. In FIG. 10, the relationship between
the engine speed and the torque shifts from Tb1 through Tb2, Tb3,
Tb4, and Tb5 to Tb6 in accordance with combustion in the
cycles.
Specifically, in the second example, the engine speed at the time
when the cranking has ended is lower than the determination
threshold value R0. Thus, the fuel injection amount in the first
combustion cycle is set to the step-over injection amount F1, which
is smaller than the jump-over injection amount F2, by the fuel
amount setting section 106 (in step S208). When the set amount of
fuel is injected and the injected fuel is burnt, the engine speed
increases, due to the torque obtained by the combustion, and
approaches the lower limit R1 of the resonance speed range Br as
indicated by the solid line connecting Tb1 and Tb2 shown in FIGS. 9
and 10.
When combustion is performed in the first combustion cycle, the
engine speed achieved by the combustion increases, as indicated by
the solid line connecting Tb1 and Tb2 shown in FIGS. 9 and 10, to a
speed higher than the determination threshold value R0 and lower
than the lower limit R1 of the resonance speed range Br. Since the
engine speed has increased to be close to the lower limit R1 of the
resonance speed range Br, due to the combustion in the first
combustion cycle, the fuel injection amount in the second
combustion cycle is set to the jump-over injection amount F2 by the
fuel setting section 106 (in step S209). When the set amount of
fuel is injected and the injected fuel is burnt, the engine speed
is increased more significantly due to the torque obtained by the
combustion, by the increased amount of the fuel injection, compared
to when the first combustion cycle is performed. The engine speed
jumps over the resonance speed range Br in this manner.
When the engine speed jumps over the resonance speed range Br, the
engine speed achieved by the combustion in the second cycle (i.e.
the second ignition) increases, as indicated by the solid line
connecting Tb2 and Tb3 shown in FIGS. 9 and 10, to a speed higher
than the upper limit R2 of the resonance speed range Br and lower
than the idle speed Ri. The fuel injection amount and how the
engine speed increases due to combustion in the third and
subsequent combustion cycles according to the second example are
the same as those in the second and subsequent combustion cycles
according to the first example described above.
Sometimes in the case in which, as in the second example, the fuel
injection amount in the first combustion cycle is set to the
maximum injection amount because the engine speed at the time when
cranking has ended is lower than the determination threshold value
R0, the engine speed achieved by the fuel injection based on the
setting and the combustion of the injected fuel may fall within the
resonance speed range Br, as indicated by the broken line
connecting T1' and T2' shown in FIGS. 9 and 10. If this happens,
the resonance generates large vibrations in the powertrain PT
including the engine 1. The vibrations of the powertrain cause
vibrations and noise in the vehicle V, which makes the occupant(s)
in the vehicle V uncomfortable.
To address this problem, the following settings are made in the
engine 1 of the present embodiment, as described in the first and
second examples. That is, the injection amount setting section 106
sets the fuel injection amount to the step-over injection amount F1
smaller than the jump-over injection amount F2, if the engine speed
is lower than the determination threshold value R0. The injection
amount setting section 106 sets the fuel injection amount to the
jump-over injection amount F2 larger than the step-over injection
amount F1, if the engine speed is higher than or equal to the
determination threshold value R0. This configuration makes it
possible to increase the engine speed such that the engine speed
approaches the lower limit R1 of the resonance speed range Br, up
to a predetermined range, and then cause the engine speed to jump
over the resonance speed range Br, while in the process of
increasing the engine speed by execution of the combustion cycles.
This reduces possible failures in jumping over the resonance speed
range Br. The resonance occurring in the powertrain PT at the start
of the engine 1 can be effectively reduced in this manner. As a
result, vibrations of the vehicle V caused by resonance in the
powertrain PT, and accompanying noise can be advantageously
reduced.
As can be seen, a preferred embodiment has been described as an
example of the technique disclosed herein. However, the technique
disclosed herein is not limited to the above embodiment, and is
also applicable to those embodiments in which changes, replacement,
addition, omission, and other modifications are made.
Alternatively, components described in the above embodiment may be
combined as another embodiment. In addition, some of the components
illustrated in the appended drawings or mentioned in the detailed
description may be unessential in solving the problem. Therefore,
such unessential components should not be taken for essential ones,
simply because such unessential components are illustrated in the
drawings or mentioned in the detailed description.
For example, the foregoing embodiment may also have the following
configurations.
The configuration of the engine 1 is a mere example, and not
limited thereto. For example, while the engine 1 includes the turbo
supercharger 61 in the embodiment, the turbo supercharger 61 may be
omitted.
While an example has been described in which the engine 1 is a
diesel engine and the fuel injection amount is adjusted to control
the torque, the configuration is not limited thereto. The engine 1
may be a spark ignition gasoline engine. In this case, the torque
of the engine 1 may be controlled by adjusting an ignition timing
in addition to or in place of the adjustment of the fuel injection
amount.
What is important is as follows. The engine speed is obtained in
each combustion cycle at the start of the engine 1. If the
difference between the engine speed and the lower limit R1 of the
resonance speed range Br is lower than a predetermined reference
value, a relatively large torque (e.g., the first torque) is set.
If the difference is larger than or equal to the reference value, a
relatively small torque (e.g., the second torque) is set. This
setting makes it possible to increase the engine speed such that
the engine speed approaches the lower limit of the resonance speed
range, up to a predetermined range, and then becomes higher than or
equal to the resonance speed range Br, while in the process of
increasing the engine speed by executing combustion cycles.
DESCRIPTION OF REFERENCE CHARACTERS
1 Engine (Compression Ignition Engine) 11a Cylinder 14 Piston 14a
Combustion Chamber 15 Crankshaft 18 Injector 91 Starter Motor 100
PCM (Controller) 101 Engine Starter 102 Speed Obtaining Section 105
Intake Air Amount Obtaining Section 106 Injection Amount Setting
Section Ri Idle Speed Rr Resonance Speed Br Resonance Speed Range
R0 Determination Threshold Value (Reference Value) R1 Lower Limit
of Resonance Speed Range R2 Upper Limit of Resonance Speed Range F1
Step-Over Injection Amount (Second Injection Amount) F2 Jump-Over
Injection Amount (First Injection Amount) F3 Resonance Induction
Reducing Amount SW1 Crank Angle Sensor (Engine Speed Sensor) SW2
Airflow Sensor SW8 Water Temperature Sensor
* * * * *